Is the friction that leads to the emission of semen during wrestling practice considered forbidden (haram), and what is the expiation for this sin?

Sexual contact that causes pleasure between men is forbidden, and it is considered a type of sodomy. Its expiation is through sincere repentance, remorse, seeking forgiveness, and increasing good deeds.

Wrestling in light clothing that exposes 'awrat (private parts) or where the wrestler feels pleasure is forbidden, as is anything that causes harm to either party. However, wrestling that involves training and developing strength and defense, with modesty and avoiding forbidden contact, is permissible.

Al-Zuhayli mentioned that freestyle wrestling, boxing, and similar activities are forbidden if they cause harm, and are permissible if there is no harm or if they accustom a person to strength, fighting, and self-defense.